Hepatitis B virus belongs to the family of hepadnaviridae. It can cause acutely and/or persistently and progressively chronic diseases. Many other clinical manifestations in the pathological morphology can be also caused by HBV—in particular chronic hepatitis, cirrhosis and hepatocellular carcinoma. Additionally, coinfection with hepatitis D virus may have adverse effects on the progress of the disease.
The conventional medicaments approved to be used for treating chronic hepatitis are interferon and lamivudine. However, the interferon has a moderate activity and a great adverse side reaction. Although lamivudine has good activity, its resistance develops rapidly during the treatment and relapse effects often appear after the treatment has stopped. The IC50 value of lamivudine (3-TC) is 300 nM (Science, 2003, 299, 893-896).
Deres, et al., have reported heteroaryl-substituted dihydropyrimidine (HAP) compounds including Bay41-4109 and Bay39-5493, and these compounds play a role in blocking HBV replication by preventing the proper formation of viral core particles (nucleocapsids). It has been demonstrated that Bay41-4109 has a better drug metabolic properties in clinical study (Science, 2003, 299, 893-896). The study of these compounds' mechanism indicated that through reacting with 113-143 amino acid residues of a core protein, heteroaryl-substituted dihydropyrimidine compounds have changed the angle between dimers which can form nucleocapsids, and thus led to forming unstably expanded nucleocapsids, which accelerate the degradation of the core protein (Biochem. Pharmacol, 2003, 66, 2273-2279).
Patent application WO2014029193 and CN201310373003.5 have disclosed a number of dihydropyrimidine (HAP) compounds having the effect of blocking replication of HBV virus, wherein the compounds of formula (IIa) and (IIb) have better activity:

In the present invention, the compound of formula (I) named (S)-4-(((R)-6-(2-chloro-4-fluorophenyl)-5-(methoxycarbonyl)-2-(thiazol-2-yl)-3,6-dihydropyrimidin-4-yl)methyl)morpholine-3-carboxylic acid was isolated from the compound of formula (IIb).

During the preparation process of the compound named (S)-4-(((R)-6-(2-chloro-4-fluorophenyl)-5-(methoxycarbonyl)-2-(thiazol-2-yl)-3,6-dihydropyrimidin-4-yl)methyl) morpholine-3-carboxylic acid, it is found that the compound, as a foamy solid, has poor flowability and certain hygroscopicity so that it is disadvantageous for keeping and weighing, which involves a number of inconveniences. Therefore, in order to find a solid form with better drugability, the applicant developed compound (I) into various acid addition salts and base addition salts through a number of experimental study and found that salified compound has significantly improved purity, physical behavior facilitating formulation, small hygroscopicity facilitating keeping and weighing, and improved solubility. Surprisingly, the applicant also obtained a complex formed from compound (I) and L-tartaric acid during the experiments. The complex has not only a simple preparation process facilitating scale-up processes but also physical behaviors facilitating formulation, high purity and good solubility. Furthermore, the complex has superior stability to keep the purity unchanged substantially under high temperature, high humidity and illumination conditions, which lead to superior drugability.